Table 1. Genotypes of candidate eex mutants.

	Mutants isolated from:
Class of FOAr mutant	BY4733	Y7092	Total no. of mutants
eex
Intragenic to pol2-4	4	1	5
Extragenic to pol2-4	50	26	76
Total	54	27	81
pol2-4 → POL2 conversion	26	3	29
Other (e.g., ura3 mutations)	23	0	23
Total	103	30	133

FOA-resistant (FOA^r) colonies from 133 different pol2-4–LEU2 POL2–URA3 msh2Δ parent clones were isolated, and POL2 was genotyped to distinguish genuine eex mutants from pol2-4 → POL2 gene conversions and other mutations that confer FOA resistance (e.g., ura3). Clones harboring only pol2-4 were considered eex mutants. Plasmids from eex mutants were recovered and retested in a fresh msh2Δ strain to distinguish second-site suppressors within pol2-4 (“intragenic eex”) from eex mutations located extragenic to pol2-4 (“chromosomal eex”). eex mutants were isolated from two different strains: BY4733 and Y7092 (Figure 3, A and B).